Signal lines may be used to carry a wide variety of electrical signals in a wide variety of systems. Examples of signal lines include wires, coaxial cables, twisted pairs, optical fibers, etc. Signal lines may carry analog signals, digital signals, encoded signals, data packets, etc.
It may be desirable in a variety of circumstances to determine a time when an electrical signal propagating on a signal line reaches a particular point along the signal line. For example, the times when an electrical signal reaches different points along a signal line may be used to determine a propagation delay of the signal line. In another example, the times when different electrical signals in a system reach different points along different signal lines in the system may be used to determine the overall timing of the system.
Oscilloscopes, logic analyzers, and similar instruments may be used to detect the presence of an electrical signal at a particular point along a signal line. Unfortunately, oscilloscopes, logic analyzers, and similar instruments are relatively complex and expensive and may not be practical to use in some environments and physical locations.